Electronic scanning device for television



Oct. 23,1945. A. P. PAUMIER 2,387,698

' ELECTRONIC SCANNING DEVICE FOR TELEVISION Y Filed May 6, 1939 AndreRaul $0im ar INVE'N O Patented Oct. 23, 1945 ELECTRONIC SCANNIN G."DEVICE FOR TELEVISION 'Andr'Paul Paumier, Sccaux,'France; vestd in theAlien Property Custodian "fapplicationMay 6, 1939,--Serial No; 272,073

In; France May 12, 1938 connected with the manner in which theiphoto-l-eleo'tric'mosaic plate is scanned with the cathoderay scanning beam.Various methods have' hithertobeen proposed for compensating or.lcor'r'e'ct- -ingithe marks :inz questionfstarting in g'eneral :fromaidevelopment of'the f parasiticmodulation function in' 'MacLaurinsprogression which is stopped atiits second Forlthird term; and experimentally adjusting-the numerical 'values and the phases of the tiandt terma' t'representing the :time, which1 are: produced by' appropriate:generators.

This correction requires accurate -adjustments which have tov be readjusted'ifromtime to time, and only gives partially satisfactoryresults. The present invention relates to a'method ofcorrecti'on-a'which isquitedifierent and the success of which has beenprovedl=by experience. It essen- =tially consists in the use-of:armagnetic correcting field of relativelys'tsmall'i amplitude; thea'ction of which may be assumed tobe exerted on the very soft-secondarylfiparas'itic) electrons'Whiah cause themarks' as has been suggested.The direction of-said magnetic fieldhas to be'substantiallypar---allel'vvith thecathode raylbeampf the icono- -scope-andinclinedfr'elatively' to the surface -'of --the scanningscreen.

"These conditions are set' forth in detail in-the ensuing descriptiontaken with reference to the accompanying "drawinglwhich shows by way ofexample an embodiment of a device according to the invention.

In the drawing, a scanning tube called iconoscope is shown. Said tube l,the actual construction of which is not a part of the invention,essentially comprises a screen 2 and a cathoderay oscillograph 3. Thescreen 2 is formed by a metal collecting plate which is separated from amosaic of photo-electric elements by an insulating plate. On said screenis projected the image to be scanned 4 by means of an optical system 5.The oscillograph essentially comprises a cathode 6, a grid 7, a firstanode 8 and a second anode 9, and also means I 0 for causing theoathode-ray beam to deviate in two directions at right angles, so as toscan the screen 2. It is of course understood that" this description-of-the: tube I is only given by-tway =of example in Border tolsillus- 5trate the present inventionand asa reference to "the arrangement of:-the F tubes --called iconoscopes to; which the present invention.relates;

EXperience has shown that byimodi-fying a con- :tinuous magnetic field,for example by means of av coil surrounding the head of the iconoscope,'it was possible to compensateimore or less "the marks-of the pictureOfWhiCh mentionwas made "above. The compensating action-is completedpr adirection of the field that makes an ang-le--.of about with the-plane-ofthe mosaic plate, or approximately parallel-with the axisof thecathode-ray oscillog-raph; this compensation becomes zero;forafieldparallel with the: plane of the mosaic plate. Finally it is onlyexerted on values .of the. brilliance of. the picture which .are..n'ottoo highfin fact, when said brilliance increases, theintensity of thecompensating field .haslto be increased,- and this quickly leads tovalues which interfere with the. s'canning of the mosaic plate. By (wayof a .nbn-limitati've example fforian iconoscope wherein the.accelerating Voltage, of the scanning beamwas of the ordr"of'1,'00O',v.and for a picture'illumination'of betweeni'l5and luxes, a compensatingfield of theorderof 1 'gauss proved "satisfactory. Said'field' may becreatedby a coil llwhich is suitably'arranged about theiconosco'pe'and-is supplied by a device 12 which supplies "it "with thenecessary current. Satisfactory results are also obtained with analternating magnetic field of appropriate form and -'frequency,-orwith-a field which is-a discontinuous function of Y thetime, forexample which isof suitable intensity at certain instants" or during"certainver'y 'short intervalsgand is Zero "outside saidintervals, the-irequ'e'nc'y of thefield being in this case preferably 1 connected tothe periodicity of the scanning, for example by controlling the deviceI2 by means of the same source of frequency which control the scanningdevice Hi.

What I claim is:

1.. A television transmitting tube comprising a mosaic screen formed bya conducting collecting surface, a mosaic of photo-electric elements, aninsulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,means for creating inside the transmitting tube a magnetic field ofsmall intensity relatively to the other fields existing in the tube, thedirection of which is substantially parallel with the electron beam andis inclined relatively to said screen,

whereby parasitic modulation of the image pro- Jected on said mosaicscreen is prevented.

2. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, an

insulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,a coil surrounding said tube, the axis of said coil being substantiallyparallel with the electron beam of the tube and inclined relatively tosaid screen, and means for sending an electric current through saidcoil, whereby a magnetic field hood of the screen, the axis of said coilbeing substantially parallel with the axis of the tube and inclinedrelatively to said screen, and means for sending an electric currentthrough said coil, whereby a magnetic field directed to said screen iscreated inside the tube, which field prevents parasitic modulation ofthe image projected on said screen.

4. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, aninsulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,means for creating inside the transmitting tube a continuous magneticfield of small intensity relatively to the other fields existing in thetube,

the direction of which is substantially parallel with the electron beamand is inclined relatively to said screen, whereby parasitic modulationof the image projected on said mosaic screen is prevented.

5. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, aninsulating plate p ing the latter from said surface, an electron gun,and deflecting means for scanning said screen by the electron beam,means for creating inside the transmitting tube an alternating magneticfield of small intensity relatively to the other fields existing in thetube, the direction of which is substantially parallel with the electronbeam and is inclined relatively to saidscreen, whereby parasiticmodulation of the image projected on said mosaic screen is prevented.

6. A television transmitting tube comprising a mosaic screen formed by aconducting collecting a means for creating inside the transmitting tubea discontinuous magnetic field of small intensity relatively to theother fields existing in the tube, the direction of which issubstantially parallel with the electron beam and is inclined relativelyto said screen, whereby parasitic modulation of the image projected onsaid mosaic screen is prevented.

7. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, aninsulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,a coil surrounding said tube, the axis of said coil being substantiallyparallel with the electron beam of the tube and inclined relatively tosaid screen, and means for sending a continuous electric current throughsaid coil, whereb a magnetic field is created inside the tube whichprevents parasitic modulation of the image projected on said screen.

8. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, aninsulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,a coil surrounding said tube, the axis of said coil being substantiallyparallel with the electron beam of the tube and inclined relatively tosaid screen, and means for sending an alternating electric currentthrough said coil, whereby a magnetic field is created inside the tubewhich prevents parasitic modulation of the image projected on saidscreen. 7

9. A television transmitting tube comprising a mosaic screen formed by aconducting collecting surface, a mosaic of photo-electric elements, aninsulating plate separating the latter from said surface, an electrongun, and deflecting means for scanning said screen by the electron beam,a coil surrounding said tube, the axis of said coil being substantiallyparallel with the electron beam of the tube and inclined relatively tosaid screen, and means for sending a discontinuous electric currentthrough said coil, whereby a magnetic field is created inside the tubewhich prevents parasitic modulation of the image projected on saidscreen.

ANDRE PAUL PAUMIER.

